U.S. patent number 4,501,522 [Application Number 06/432,759] was granted by the patent office on 1985-02-26 for manipulator.
This patent grant is currently assigned to United Kingdom Atomic Energy Authority. Invention is credited to Roy Causer, Donald Orr.
United States Patent |
4,501,522 |
Causer , et al. |
February 26, 1985 |
Manipulator
Abstract
A manipulator for remote handling in a hostile environment 14,
has a slave arm 10 comprising an upper arm 30, a forearm 52 and a
jaw mechanism 60. The upper arm 30 is pivotally suspended from a
shoulder support 20 and is telescopically extendible such that
straight line motion of the forearm 52 is readily obtained. In
addition the forearm 52 is arranged to pivot relative to the upper
arm 30 through the same angle as the upper arm 30 but in the
opposite sense such that the forearm 52 maintains a constant
orientation when the upper arm 30 pivots. All the motions of the
slave arm 10 may be controlled through mechanical linkages from a
drive unit 18 situated outside the hostile environment 14, and
extending through shielding 13 into the environment 14.
Inventors: |
Causer; Roy (Wantage,
GB2), Orr; Donald (Didcot, GB2) |
Assignee: |
United Kingdom Atomic Energy
Authority (London, GB2)
|
Family
ID: |
10525406 |
Appl.
No.: |
06/432,759 |
Filed: |
October 4, 1982 |
Foreign Application Priority Data
|
|
|
|
|
Oct 26, 1981 [GB] |
|
|
8132260 |
|
Current U.S.
Class: |
414/4; 414/718;
414/735; 901/18; 901/25 |
Current CPC
Class: |
B25J
3/04 (20130101); B25J 9/046 (20130101); B25J
18/025 (20130101); B25J 17/0283 (20130101); B25J
18/00 (20130101); B25J 9/10 (20130101) |
Current International
Class: |
B25J
9/04 (20060101); B25J 17/02 (20060101); B25J
3/04 (20060101); B25J 18/02 (20060101); B25J
18/00 (20060101); B25J 9/10 (20060101); B25J
9/02 (20060101); B25J 3/00 (20060101); B25J
003/04 () |
Field of
Search: |
;414/1-8,730,718,719,732,735 ;901/18,25 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1475018 |
|
Mar 1967 |
|
FR |
|
418762 |
|
Feb 1967 |
|
CH |
|
2022046 |
|
Dec 1979 |
|
GB |
|
Primary Examiner: Spar; Robert J.
Assistant Examiner: Siemens; Terrance L.
Attorney, Agent or Firm: Hinds; William R.
Claims
We claim:
1. A manipulator including a slave arm comprising, a support means
defining a first pivotal connection; an upper arm portion of the
slave arm arranged to be supported by the first pivotal connection
at an intermediate position along the length of the upper arm
portion, and defining a second pivotal connection at one end of the
upper arm portion and defining a movable connection at or near the
other end of the upper arm portion, the axes of the first and of
the second pivotal connection being substantially parallel; a
forearm portion of the slave arm connected at one end to the second
pivotal connection; pivoting means connected to the movable
connection for pivoting the upper arm portion about the first
pivotal connection, and drive means for moving the pivoting means;
the distances of the second pivotal connection and of the movable
connection from the first pivotal connection being variable but
such that the ratio of the distances between the first and the
second pivotal connections and between the first pivotal connection
and the movable connection, is maintained substantially constant,
and the slave arm being arranged so that pivotal movement of the
upper arm portion about the first pivotal connection produces
pivotal movement of the forearm portion about the second pivotal
connection through the same angle as the pivotal movement of the
upper arm portion but in the reverse direction.
2. A manipulator as claimed in claim 1, wherein the movable
connection and the second pivotal connection are slidable along the
upper arm portion.
3. A manipulator as claimed in claim 2, wherein the movable
connection lies substantially in the plane defined by the axes of
the first and the second pivotal connections.
4. A manipulator as claimed in claim 3, wherein the movable
connection is pivotally connected to the pivoting means, having a
pivotal axis substantially parallel to the axes of the first and
the second pivotal connections.
5. A manipulator as claimed in claim 4, wherein the pivoting means
is movable in two mutually perpendicular directions in a plane
perpendicular to the axes of the first and the second pivotal
connections.
6. A manipulator as claimed in claim 1, wherein an elongate member
extends from the movable connection along the upper arm portion and
defines a rack along a portion of the length of the elongate
member, a rack member is connected to the second pivotal connection
and extends along the upper arm portion, and compound gear means
engage the rack and the rack member so that movement of the
elongate member produces movement of the rack member and thereby of
the second pivotal connection in the reverse direction and such as
to maintain said ratio of distances.
7. A manipulator as claimed in claim 6, wherein the upper arm
portion is of telescopic construction and the rack member comprises
a telescopic member of the upper arm portion defining a rack along
a portion thereof.
8. A manipulator as claimed in claim 1, wherein the upper arm
portion incorporates a plurality of drives to movements of the
forearm portion.
9. A manipulator as claimed in claim 8, wherein the upper arm
portion comprises two members extending parallel to one another
from the first pivotal connection to the second pivotal connection,
each said member being of telescopic construction and incorporating
some of the drives to movements of the forearm portion.
10. A manipulator as claimed in claim 8 wherein each drive
comprises a telescopic rotary drive shaft drivable by gears at the
ends thereof, and comprising two shafts with opposing splines
telescopically slidable with respect to each other.
11. A manipulator as claimed in claim 10, wherein the drives
comprise telescopic rotary drive shafts arranged concentrically
around each other.
12. A manipulator as claimed in claim 8, wherein the drive means
comprises a drive assembly, and a plurality of drives to movements
of the pivoting means and of the forearm portion, a single motor
and gear trains arranged to be driven by the motor and connected to
the drives, the gear trains including pairs of magnetic particle
clutches in parallel to engage or disengage a movement in a
selected direction.
13. A manipulator as claimed in claim 12, wherein the drive
assembly is located outside a hostile environment in which the
slave arm is to be used, and sealed drive members extend through an
enclosure about the hostile environment from the drive
assembly.
14. A manipulator as claimed in claim 8, wherein the forearm
portion includes a jaw mechanism rotatable about the longitudinal
axis of the forearm portion, and about the longitudinal axis of the
jaw mechanism.
15. A manipulator as claimed in claim 14, wherein the jaw mechanism
is also rotatable about an axis set at an angle to the longitudinal
axis of the forearm portion and at an angle to the longitudinal
axis of the jaw mechanism.
16. A manipulator as claimed in claim 15 wherein both the angles
are the same at about 45.degree..
17. A manipulator as claimed in claim 1 in combination with a
sealed enclosure through a wall of which the manipulator extends.
Description
This invention relates to manipulators used for handling objects
remotely, for example in a hostile environment.
Such manipulators typically include a variable length slave arm
suspended at one end and which is usually capable of providing
three distinct angular movements. A jaw mechanism is conventionally
mounted at a wrist portion at the other end of the slave arm, and
one of the problems associated with such manipulators is that of
managing to keep the jaw mechanism at the same attitude with
respect to the ground and performing straightline movement with
angular movement of the slave arm.
According to the present invention, there is provided a manipulator
including a slave arm comprising, a support means defining a first
pivotal connection; an upper arm portion of the slave arm arranged
to be supported by the first pivotal connection at an intermediate
position along the length of the upper arm portion and defining a
second pivotal connection at one end of the upper arm portion and a
movable connection at or near the other end of the upper arm
portion, the axes of the first and of the second pivotal
connections being substantially parallel; a forearm portion of the
slave arm connected at one end to the second pivotal connection;
pivoting means connected to the movable connection for pivoting the
upper arm portion about the first pivotal connection, and drive
means for moving the pivoting means; the distances of the second
pivotal connection and of the movable connection from the first
pivotal connection being variable but such that the ratio of the
distances between the first and the second pivotal connections, and
between the first pivotal connection and the movable connection, is
maintained substantially constant, and the slave arm being arranged
so that pivotal movement of the upper arm portion about the first
pivotal connection produces pivotal movement of the forearm portion
about the second pivotal connection through the same angle as the
pivotal movement of the upper arm portion but in the reverse
direction.
The movable connection and the second pivotal connection may be
arranged to slide along the upper arm portion which is desirably of
telescopic construction, sliding of the movable connection causing
telescopic movement of the upper arm portion. The pivoting means
may be movable in two mutually perpendicular directions in a plane
perpendicular to the pivotal axes of the first and the second
pivotal connections. Desirably, all movements of the slave arm are
driven from a drive assembly and a plurality of drives to these
movements arranged to be energised by the drive assembly from a
single motor through gear trains which include pairs of magnetic
particle clutches in parallel to engage or disengage a required
movement in a selected direction.
In the preferred form of the invention, the drive assembly is
arranged to be mounted outside a hostile environment in which the
slave arm is to be used, and sealed members extend through an
enclosure about the hostile environment from the drive
assembly.
The invention will now be further described by way of example only
and with reference to the accompanying drawings, in which:
FIG. 1 shows a perspective view of a manipulator slave arm;
FIG. 2 shows a sectional view on the line II--II of FIG. 1;
FIG. 2a shows a sectional view on the line IIa--IIa of FIG. 2;
FIG. 3 shows a sectional view on the line III--III of FIG. 2;
FIG. 3a shows a sectional view on the line IIIa--IIIa of FIG.
3;
FIG. 4 shows a sectional view on the line IV--IV of FIG. 1;
FIG. 5 shows a sectional view on the line V--V of FIG. 4;
FIG. 5a shows a perspective view in the direction of arrow A of
FIG. 5;
FIG. 6 shows a modified sectional view on the line VI--VI of FIG.
4;
FIG. 7 shows a sectional view on the line VII--VII of FIG. 6;
FIG. 8 shows a perspective view of an alternative manipulator slave
arm;
FIG. 8a shows a perspective view, partly broken away and to an
enlarged scale, in the direction of arrow A of FIG. 8;
FIG. 8b shows part of a view, partly broken away and to an enlarged
scale, in the direction of arrow B of FIG. 8;
FIG. 9 shows a sectional view on the line IX--IX of FIG. 8b;
FIG. 10 shows another part of the view in the direction of arrow B
of FIG. 8, in medial section;
FIG. 11 shows a perspective view of another alternative manipulator
slave arm; and
FIG. 12 shows a partial sectional view, to an enlarged scale, in
the direction of arrows XII of FIG. 11.
Referring now to FIG. 1, a manipulator slave arm 10 is shown
secured to a sealed cylindrical plug 12 in a roof 13 of a
radioactive cell 14. Sealed drives (not shown) to the slave arm 10
are provided through the plug 12 from a demountable drive assembly
18. Two support beams 20 extend down from the base of the plug 12,
having upwardly extending central slots 22 at the lower end of each
support beam 20 and holes 24 through each support beam 20 along an
axis Y--Y to locate shoulder pivot pins 26. The slave arm 10 has an
upper arm 30 comprising two parallel telescopic members 32a, 32b
respectively supported by the support beams 20 and which are
pivotable in pitch `P` about the axis Y--Y.
As shown in more detail in FIG. 5a to which reference is made, the
upper ends of the telescopic members 32a, 32b, define slides 34
which support respective sliding blocks 36 between which a control
pivot pin 42 extends along an axis Z--Z parallel to the axis Y--Y
and locates in a control member 40 capable of vertical and
horizontal displacement. The lower ends of the telescopic members
32a, 32b are joined by a lower bridging member 38 and by an elbow
pivot pin 50 on an axis X--X parallel to the axis Y--Y. The
extension of the telescopic members 32a, 32b is arranged such that
the distance from the axis Y--Y to the axis X--X bears a constant
ratio to the distance from the axis Y--Y to the axis Z--Z, and such
that the axes X--X, Y--Y, Z--Z remain co-planar. Hence motion of
the control member 40 generally produces simultaneous pitching P
and extension E of the upper arm 30.
The elbow pivot pin 50 supports a forearm 52 which is pivotable
about the axis X--X as shown by arrow V of FIG. 1. At the lower end
of the forearm 52 is a wrist pivot pin 54 extending perpendicular
to the longitudinal axis of the forearm 52, which supports a jaw
mechanism 60. The jaw mechanism 60 can turn G about its
longitudinal axis; it can turn T about the longitudinal axis of the
forearm 52; and can pivot W about the axis of the wrist pivot pin
54, and comprises a pair of jaws 62 supported by a parallel motion
linkage 64 to provide prehensile motion `J` of the jaws 62.
The motions of the component parts of the slave arm 10 can be
summarised as follows:
(i) the slave arm 10 can slew S about the longitudinal axis of the
plug 12;
(ii) the upper arm 30 can pitch P about the axis Y--Y, and is
extendible E;
(iii) the forearm 52 can pivot V about the axis X--X;
(iv) the jaw mechanism 60 can turn G about its longitudinal axis,
can pivot W about the axis of the wrist pivot pin 54, and can turn
T about the longitudinal axis of the forearm 52; and
(v) the jaws 62 can move J in a prehensile manner.
Referring now to FIG. 2, the plug 12 comprises an outer cylindrical
sleeve 70, and an inner casing 72 filled with a shielding material
74 which may comprise polyethylene or lead depending on the nature
of the radiation from within the cell 14. The inner casing 72 is
rotatably located in the outer sleeve 70 by ball bearings 75a, 75b,
and near the top of the outer sleeve 70 is an internal gear 76
which extends around the inner circumference of the outer sleeve 70
and engages a gear pinion 78 rotatably mounted on the inner casing
72. Rotation of the pinion 78 by means of a shaft 79 and drive
means (not shown) through a demountable coupling 90, rotates the
inner casing 72 relative to the outer sleeve 70, thus providing
slew motion of the slave arm 10.
As shown in more detail in FIG. 2a, the control member 40, which
locates the control pivot pin 42 in a cylindrical hole 44, is
slidably supported in a slideway 46 on the underside of a support
bar 48, and can be driven horizontally by a lead screw 47 which
engages the control member 40 and is supported at each end by
bearings 49 attached to the support bar 48.
Drives for horizontal and vertical motion of the control member 40
are by means of drive shafts 16a, 16b, 16c passing through channels
84a, 84b, 85 in the shielding material 74 and driven at their upper
ends by the drive assembly 18 through demountable couplings 90a,
90b, 90c respectively which incorporate rotary seals (not shown).
The drive shaft 16c for horizontal motion of the control member 40
comprises a splined shaft 82 and a corresponding internally splined
hollow shaft 83, passing at its lower end through a bearing 92 in
the support bar 48, and drivably connected to the lead screw 47 by
bevel gears 93. The two drive shafts 16a and 16b for vertical
motion of the control member 40 are identical, and each comprises a
threaded shaft 95 engaging in an internally threaded hollow column
96 guided in its vertical motion by a recirculating ball bushing 98
and secured at its lower end to the support bar 48.
The drive assembly 18 is mounted on a plate 128 and comprises an
electric motor 100 connected to a shaft 102 on which a forward
bevel gear 104 and a reverse bevel gear 105 are mounted, each
motion of the slave arm 10 being driven by the motor 100 through a
corresponding clutch system 106, 107 (only those for vertical and
horizontal motions of the control member 40 are shown). The clutch
systems 106, 107 are identical and each comprises two bevel gears
108, 109 on parallel shafts 110, 112 and engaging respectively with
the forward bevel gear 104 and the reverse bevel gear 105, each
bevel gear 108, 109 being connected through a magnetic particle
clutch 114, 115 and a shaft 110m, 112m respectively to a toothed
wheel 116, 117, the toothed wheels 116 and 117 being linked
together by a toothed belt 118. Suitable magnetic particle clutches
114, 115, and referred to as variable torque couplings, may be
obtained from Smiths Industries Limited, Industrial Instruments
Division, Waterloo Road, Cricklewood, London, NW2 7UR, England.
Adjacent and drivably connected to one toothed wheel 116 of each
clutch system 106, 107 is a second toothed wheel 120a, 120c linked
by a toothed belt 122a, 122c to a toothed wheel 124a, 124c on an
output drive shaft 126, 127. The output drive shafts 126, 127 are
drivably connected to the drive shafts 16a, 16b, 16c through pairs
of bevel gears 130 and 131, 132 and 133, 134 and 135, and through
the demountable couplings 90a, 90b, 90c.
When the motor 100 is energised, the shaft 102 rotates, and in each
clutch system 106, 107 the two shafts 110, 112 rotate in opposite
directions. Each magnetic particle clutch 114, 115 is operated
electrically, and when energised transmits the drive from the shaft
110 or 112 on one side of the clutch 114, 115 to the shaft 110m or
112m on the other side. The direction of rotation of the toothed
wheel 116 in each clutch system 106, 107 and hence of the drive
shafts 16a, 16b, 16c, is thus determined by which of the magnetic
particle clutches 114, 115 is energised in the corresponding clutch
system 106, 107. If the clutch 114, 115 is not energised, the shaft
110m, 112m on the non-driven side of the clutch 114, 115 is free to
rotate.
Rotation of each threaded shaft 95 causes vertical motion of the
hollow columns 96 and hence of the support bar 48 and control
member 40, and rotation of the hollow shaft 83 causes rotation of
the lead screw 47 by the bevel gears 93, and hence horizontal
motion of the control member 40.
Referring now to FIG. 3 and FIG. 3a, the slave arm 10 (omitted for
clarity) is suspended from each support beam 20 by bearings 150
around opposing hollow bosses 152 on the inside of the slots 22 and
the drives through the plug 12 to other motions of the slave arm 10
are by means of identical rotary drive shafts 16d, 16e, 16f, 16g,
each of which is driven at its upper end in exactly the same manner
as described above in relation to shaft 16c, through a bevel gear
136, 137, 138, 139 (the mating bevel gears being omitted for
clarity) and a demountable coupling 90 incorporating a rotary seal
(not shown), and is rotatably mounted in a bearing 140 near its
lower end. Each shaft 16d, 16e, 16f, 16g terminates in a worm 154,
155 respectively engaging with a worm wheel 156, 157 supported by
the shoulder pivot pin 26, one worm wheel 156, or 157 being mounted
on either side of the slot 22 of each support beam 20. Each worm
wheel 156, 157 is drivably and coaxially mounted on a hypoid gear
wheel 158, 159 engaging with a hypoid gear 222, 220 (see FIG. 6)
within the slave arm 10 (not shown).
Mounted onto each drive shaft 16a . . . 16g above the demountable
couplings 90, is an incremental shaft encoder 160 (only that of
shaft 16d is shown) having a pair of detectors 162 placed in phase
quadrature relationship by means of which the direction and rate of
rotation of the respective drive shaft 16a . . . 16g may be
determined.
Referring to FIGS. 4, 5 and 6, the angular orientation of the upper
arm 30 and the forearm 52 being changed in FIG. 6, each telescopic
member 32a, 32b comprises an upper telescopic portion 200 and a
lower telescopic portion 202 slidable therein, the lower telescopic
portions 202 of the two telescopic members 32a, 32b being linked by
the lower bridging member 38, and the upper telescopic portions 200
being linked by a hollow upper bridging member 206.
Referring in particular to FIG. 6, each telescopic member 32a, 32b,
contains two rotary drive shaft assemblies 208, 211, each
comprising a splined shaft 209, 212 and a corresponding internally
splined hollow shaft 210, 213, each hollow shaft 210, 213 being
rotatably mounted in bearings 215, 216 in the upper telescopic
portion 200, and each splined shaft 209, 212 being rotatably
mounted in bearings 218, 219 in the lower telescopic portion 202.
The upper end of each drive shaft assembly 208, 211 defines a
hypoid gear 220, 222, one hypoid gear 220 engaging with the hypoid
gear wheel 159 at the adjacent side of the support beam 20, and the
other hypoid gear 222 engaging with the corresponding hypoid gear
wheel 158 (not shown) on the other side of the upper arm 30.
Similarly, near the lower end of each drive shaft assembly 208, 211
there is a hypoid gear 224, 226, one hypoid gear 226 engaging with
a hypoid gear wheel 234 (see FIG. 7) mounted on a hollow axle 225a
rotatable about the elbow pivot pin 50, the other hypoid gear 224
engaging with a hypoid gear wheel 230a rotatable about the hollow
axle 225a.
As shown in FIG. 5a, pivotally attached to the control pivot pin 42
is a yoke 260 to which are attached two parallel rods 262, which
pass in between the two support beams 20 and, as shown in FIGS. 4
and 5, extend through holes 263 through the upper bridging member
206. That portion of each rod 262 remote from the yoke 260 is
shaped to define a gear rack 264, along its upper surface, each
rack 264 engaging with a respective gear pinion 266 mounted on an
axle 268 within the upper bridging member 206. The axle 268 is
rotatably supported at each end by bearings 270 fixed to the sides
of the upper bridging member 206, and at its mid point has a larger
gear pinion 272 engaging with a rack 274 which extends through
clearance holes 276 through the upper bridging member 206 and at
one end is secured to the lower bridging member 38. ##EQU1##
Thus, in operation, in whatever direction the control member 40 and
hence the control pivot pin 42 is moved relative to the shoulder
pivot pin 26, the elbow pivot pin 50 undergoes the same motion
relative to the shoulder pivot pin 26, the distances moved by the
elbow pivot pin 50 and the control pivot pin 42 being in the above
ratio. Thus if the control pivot pin 42 moves towards (or away
from) the shoulder pivot pin 26, then the blocks 36 will slide
along the slides 34, and the racks 264 will move rotating the
pinions 266 and hence the larger pinion 272, so moving the rack 274
in the opposite direction. Hence the lower telescopic portions 202
are caused to move relative to the upper telescopic portions 200,
causing the elbow pivot pin 50 to move towards (or away from) the
shoulder pivot pin 26, the distance moved by the elbow pivot pin 50
being greater by the above ratio than the distance moved by the
control pivot pin 42. On the other hand if the control pivot pin 42
moves along an arc of a circle centred on the shoulder pivot pin
26, so too will the elbow pin 50, through the same angle, and the
upper arm 30 will not vary in length.
Referring to FIG. 7, from which drive means inside the forearm 52
for motions of the jaw mechanism 60 and the jaws 62 have been
omitted, cylindrical hollow members 280 extend from the sides at
the ends of the lower telescopic portions 202 and support bearings
282 about which a housing 283 for the forearm 52 locates, thereby
enabling the forearm 52 to turn about the axis X--X. The elbow
pivot pin 50 is secured at each end to circular end caps 284
closing circular apertures 286 in the sides of the lower telescopic
portions 202. Near the ends of the drive shaft assemblies 211 are
the hypoid gears 226 engaging with the hypoid gear wheels 234 which
are mounted on the hollow axles 225a, 225b rotatable about the
elbow pivot pin 50 and near the ends of the drive shaft assemblies
208 are the hypoid gears 224 engaging with the hypoid gear wheels
230a, 230b which are rotatable about the hollow axles 225a, 225b.
The hypoid gear wheel 230a extends from one end of a hollow shaft
portion 240, rotatable about the hollow axle 225a, and having a
bevel gear 243 at its other end. A hollow shaft 241 extending at
one end from the hypoid gear wheel 230b, has a bevel gear 245 at
its other end. The forearm 52 locates in a spigot portion 285 of
the housing 283 and is rotatable in spaced-apart bearings 287, a
bevel gear 289 at the upper end of the forearm 52 engaging the
bevel gears 243, 245. Thus the drive to cause the slave arm 10 to
bend, i.e. to cause the forearm 52 to turn about the axis X--X, or
to rotate in the bearings 287 (referring to FIGS. 3, 3a, 6 and 7)
takes place from the drive assembly 18, through the bevel gears
137, 138, the rotary drive shafts 16e, 16f, the worms 155, the worm
wheels 157 and the hypoid gear wheels 159, causing rotation of the
hypoid gears 220, the rotary drive shaft assemblies 208 and the
hypoid gears 224 and so turning the hypoid gear wheels 230a, 230b,
the hollow shaft portions 240, 241 and thus the bevel gears 243,
245. If the bevel gears 243, 245 are driven in the same direction,
the forearm 52 is turned about the axis X--X, but if driven at the
same speed in opposite directions, the forearm 52 rotates in the
bearings 287.
Referring also to FIG. 1, if the forearm 52 is at a desired
orientation, and the upper arm 30 pivots in pitch motion P about
the shoulder axis Y--Y, then the frictional resistance between the
worms 155 and the worm wheels 157 inhibits the worm wheels 157 and
therefore the hypoid gear wheels 159 from turning. Hence, pitch
motion P of the upper arm 30 produces rotation of the hypoid gears
220 and of the rotary drive shaft assemblies 208 about their
longitudinal axes, which turns the hypoid gears 224, the hypoid
gear wheels 230a, 230b the hollow shaft portions 240, 241 and the
bevel gears 243, 245 and so turns the forearm 52 about the axis
X--X. The hypoid gear wheels 159 and 230a, 230b and the hypoid
gears 220 and 224 are shaped so that, through whatever angle the
upper arm 30 pivots about the axis Y--Y, the forearm 52 turns
through the same angle but in the opposite sense about the axis
X--X, so maintaining the forearm 52 in its desired orientation.
Drives to the motions of the jaw mechanism 60 can be derived from
the rotation of the hollow axles 225a and 225b which are driven in
a similar manner to that of the hollow shaft portions 240, 241. An
additional actuating drive (not shown) for the jaws 62 may be
driven hydraulically or pneumatically, or may be derived from
rotation of the elbow pivot pin 50 for example by a flexible drive
shaft.
It will be understood that, in place of the hypoid gears mentioned,
other suitable right angle gear drives such as bevels may be used.
For example as shown in FIG. 8, to which reference is now made, an
alternative manipulator slave arm 300, similar to that of FIG. 1,
is shown secured to the sealed cylindrical plug 12 in the roof 13
of the radioactive cell 14 and connected to the demountable drive
unit 18 of FIG. 1. Sealed drives 16a-g (see FIGS. 2 and 3) to the
slave arm 300 extend through the plug 12 from the demountable drive
assembly 18. Two support beams 302 extend down from the base of the
plug 12, and have a hole 304 at the lower end of each beam 302
along an axis Y--Y to locate a shoulder pivot pin 306. The slave
arm 300 has an upper arm 310 comprising two parallel telescopic
members 312a, 312b respectively pivotable in pitch motion P about
the axis Y--Y.
As shown in more detail in FIG. 8a to which reference is made, the
upper ends of the telescopic members 312a, 312b define slides 314
which support respective sliding blocks 316 between which a control
pivot pin 320 extends along an axis Z--Z parallel to the axis Y--Y,
the control pivot pin 320 locating in a control member 40 capable
of vertical and horizontal displacement and being identical to the
control member 40 of FIG. 2. The lower ends of the telescopic
members 312a, 312b as shown in FIG. 8 are joined by an elbow pivot
pin 50 on an axis X--X parallel to the axis Y--Y, and supporting a
forearm 330. At the lower end of the forearm 330 is a wrist pivot
pin 54 supporting a jaw mechanism 60 identical to that of FIG. 1.
The motions of the component parts of the slave arm 300 are the
same as those of the component parts of the slave arm 10 of FIG. 1.
In particular, the forearm 330 can pivot V about the axis X--X, and
the upper arm 310 can pitch P about the axis Y--Y, and is
extensible E. The extension of the telescopic members 312a, 312b is
arranged such that the distance from the axis Y--Y to the axis X--X
bears a constant ratio to the distance from the axis Y--Y to the
axis Z--Z, and such that the axes X--X, Y--Y, and Z--Z remain in a
common plane.
Each of the telescopic members 312a, 312b comprises an upper
tubular portion 332, and a lower tubular portion 334 slidable in
the upper tubular portion 332. Each upper tubular portion 332
extends from a respective rectangular casing 336 from which the
respective slide 314 extends. As shown more clearly in FIG. 8b, the
casings 336 are linked by a central portion 338 of the shoulder
pivot pin 306, and are rotatably supported both by the shoulder
pivot pin 306 whose ends are located in bearings 340 in the holes
304 at the lower end of each beam 302, and by bearings 342 between
hollow bosses 344 and 346 of the casings 336 and the beams 302
respectively (only those supporting the telescopic member 312a
being shown). At an intermediate position along their length the
upper tubular portions 332 are linked by a hollow aluminium
bridging member 350.
As shown in FIG. 8a, pivotally attached to the control pivot pin
320 is a yoke 360, to which is attached a rod 362 which passes (as
shown in FIG. 8b) through a hole 364 through the central portion
338 of the shoulder pivot pin 306 into a rectangular housing 370.
The housing 370 extends between the central portion 338 of the
shoulder pivot pin 306 and the bridging member 350, and a second
rectangular housing 372 extends beyond the bridging member 350. To
the end of the rod 362 inside the housing 370 are attached, by
means of a shoulder pin 376 through the rod 362, two generally
rectangular, steel, double-sided rack members 388, spaced apart,
one above the other by the pin 376 as shown in FIG. 9, to which
reference is now made. The rack members 388 extend through the
bridging member 350 into the housing 372, and are joined by a
shoulder pin 390 at their ends remote from the rod 362. Along both
sides of each rack member 388 is defined a set of rack teeth 400,
each set of rack teeth 400 engaging with a respective small pinion
402. The pinions 402 are mounted on two parallel shafts 404
rotatably supported at their ends by bearings 406 in the bridge
member 350, and a gear wheel 410 is mounted on each shaft 404
between the two pinions 402. The two gear wheels 410 mesh together,
and each extends through a respective slot 412 in the adjacent
upper tubular portion 332 to engage with a rack 414 defined on the
outside of the adjacent lower tubular portion 334. Along one face
of each rack member 388 is a groove 418 in which a phosphor-bronze
guide block 420 attached to the bridging member 350 is slidably
located. ##EQU2##
Hence in operation of the slave arm 300, in whatever direction the
control member 40 and hence the control pivot pin 320 is moved
relative to the shoulder pivot pin 306, the elbow pivot pin 50
undergoes the same motion relative to the shoulder pivot pin 306,
the distances moved by the elbow pivot pin 50 and the control pivot
pin 320 being in the above ratio. Thus if the control pivot pin 320
moves towards (or away from) the shoulder pivot pin 306, then the
blocks 316 will slide along the slides 314, and the rod 362 and
rack members 388 will move and rotate the pinions 402, the guide
blocks 420 sliding along the grooves 418, so rotating the gear
wheels 410 and causing the lower tubular portions 334 to move in
the opposite direction. Consequently the elbow pivot pin 50 moves
towards (or away from) the shoulder pivot pin 306, and the upper
arm 310 shortens (or lengthens) E. On the other hand, if the
control pivot pin 320 moves along a circular arc centred on the
shoulder pivot pin 306, so too will the elbow pivot pin 50, and
through the same angle. The upper arm 310 will not vary in length,
but will undergo pitch motion P, turning about the bearings 340 and
342.
The other motions of the slave arm 300 are derived from the drive
shafts 16d, 16e, 16f and 16g. Referring again to FIG. 8a, the lower
end of each of the drive shafts 16d, 16e defines a worm 154, 155
which engages a respective worm wheel 430, 432 on a respective
shaft 434 rotatably supported by bearings 436 (only one is shown)
at the lower end of the support beam 302, the two shafts 434 being
parallel to the axis Y--Y. Also mounted on each shaft 434 is a gear
wheel 438, 440. The gear wheel 438 engages a gear 442 defined at
one end of a bobbin-shaped member 444 rotatably mounted on the
shoulder pivot pin 306, and the gear wheel 440 engages a gear 448
defined at one end of a bobbin-shaped member 450 rotably mounted on
the member 444.
Referring now to FIG. 8b, the other end of each of the members 444
and 450 defines a spiral bevel gear 445 and 451 respectively, that
engages a spiral bevel gear 446 and 452 respectively. The gear 452
is defined at one end of a short tubular shaft 454 rotatably
supported by a bearing 455 through a hole 456 in the casing 336,
and the bevel gear 446 is defined at one end of a short shaft 458
rotatably supported by two spaced-apart bearings 459 inside the
short tubular shaft 454. The other ends of the short shaft 458 and
of the short tubular shaft 454 are connected to the ends of
respective telescopic rotary drive shafts 460 and 462 extending
concentrically along the length of the telescopic member 312a and
rotatable with respect thereto. The drive shaft 460 comprises an
internally splined tube 464 drivably connected at one end by the
short shaft 458 to the bevel gear 446, and an externally splined
rod 466 telescopically slidable therein guided by steel balls 468
located between opposing splines. The drive shaft 462 is rotatable
about the drive shaft 460 and comprises an internally splined tube
470 drivably connected at one end by the short tubular shaft 454 to
the bevel gear 452, and an externally splined tube 472
telescopically slidable therein and guided by steel balls 474
located between opposing splines.
The drives through the telescopic member 312b from the drive shafts
16g and 16f are identical to the drives through the telescopic
member 312a from the drive shafts 16d and 16e.
Referring now to FIG. 10 (in which the forearm 330 is shown
colinear with the upper arm 310 for clarity), the lower tubular
portions 334 of the telescopic members 312a and 312b are attached
to casing portions 480 linked by the elbow pivot pin 50 which is
rotatably mounted in bearings 482 at each end, and by a generally
cylindrical forearm support casing 484 rotatably supported by
bearings 486 on hollow opposed bosses 488 on the casing portions
480. The splined rods 466 are rotatably supported within the
splined tubes 472 by bearings 490, and the splined tubes 472 are
rotatably supported by bearings 492 in the casing portions 480. The
splined rods 466 and the splined tubes 472 terminate in spiral
bevel gears 494, 496 within the casing portions 480.
Each bevel gear 494 engages a bevel gear 498 defined at one end of
a bobbin-shaped member 500 or 502 rotatably mounted on the elbow
pivot pin 50. The other end of each member 500 or 502 defines a
respective spiral bevel gear 508 or 510 which engages a bevel gear
512 or 514 at one end of a respective tubular drive shaft 516 or
518 extending concentrically along the length of the forearm 330,
and rotatable about the axis thereof.
Each bevel gear 496 engages a bevel gear 506 defined at one end of
a bobbin-shaped member 520 rotatably mounted about the member 500
or 502, the other end of each member 520 defining a spiral bevel
gear 526. The bevel gears 526 engage diametrically opposite
portions of a single spiral bevel gear 528 defined at one end of a
forearm tube 530, rotatable about the drive shaft 516. The forearm
tube 530 is rotatably supported by a bearing 532 at the open end of
a tubular forearm portion 534 of the forearm support casing
484.
A bevel gear 538 is mounted on the elbow pivot pin 50, and engages
a bevel gear 540 at one end of a drive shaft 542 extending axially
and rotatably along the forearm 330 inside the tubular drive shaft
518.
Thus in operation of the slave arm 300, rotation of the drive shaft
16e by the drive assembly 18 causes rotation of the worm 155, the
worm wheel 432, the gear wheel 440, the member 450, the bevel gear
452 and consequently the telescopic rotary drive shaft 462 in the
telescopic member 312a. Similarly, rotation of the drive shaft 16f
leads to rotation of the telescopic rotary drive shaft 462 in the
telescopic member 312b. Rotation of the shafts 462 causes rotation
of the bevel gears 496 and the members 520, and of the bevel gears
526. Rotation of the bevel gears 526 in opposite directions but at
the same speed causes the forearm tube 530 to turn about its own
axis, rotating in the bearing 532, so producing turning motion T of
the jaw mechanism 60 (see FIG. 8). Rotation of the bevel gears 526
in the same direction and at the same speed, however, causes the
forearm tube 530 and the forearm support casing 484 to pivot about
the axis X--X, rotating in the bearing 486, so producing pivoting
motion V of the forearm 330.
If the forearm 330 is at a desired orientation and the upper arm
310 pivots in pitch motion P about the shoulder axis Y--Y, then the
frictional resistance between the worms 155 and the worm wheels 432
inhibits both the worm wheels 432 and therefore the members 450
from rotating (only those driven by the drive shaft 16e being shown
in FIG. 8a). Hence pitch motion P of the upper arm 310 causes
rotation of the bevel gears 452 and telescopic rotary drive shafts
462, leading as described above to rotation of the bevel gears 526
in the same direction and at the same speed, so pivoting the
forearm 330 about the axis X--X. The bevel gears 451, 452 and 496,
506 have pitch diameters such that, through whatever angle the
upper arm 310 pivots about the axis Y--Y, the forearm 330 pivots
through the same angle but in the opposite sense about the axis
X--X, so maintaining the forearm 330 in its desired
orientation.
Rotation of the drive shaft 16d by the drive assembly 18 causes
rotation of the worm 154, the worm wheel 430, the gear wheel 438,
the member 444, the bevel gears 445, 446 and consequently the
telescopic rotary drive shaft 460 in the telescopic member 312a.
Similarly, rotation of the drive shaft 16g leads to rotation of the
telescopic rotary drive shaft 460 in the telescopic member 312b.
Rotation of the telescopic rotary drive shafts 460 causes rotation
of the bevel gears 494 and the members 500 and 502 respectively,
and hence rotation of the tubular drive shafts 516 and 518
respectively which are used to actuate the motions W and G of the
jaw mechanism 60.
Drives to the jaws 62 are provided by rotation of the axial drive
shaft 542, brought about by rotation of the elbow pivot pin 50.
This may be produced for example by a flexible drive shaft (not
shown), or by an electric motor (not shown).
Alternatively the rotary drive shaft 460 in the telescopic member
312a may be tubular, and a telescopic rotary drive shaft (not
shown) may be rotatably supported therein drivably connected to the
elbow pivot pin 50 by bevel gears (not shown).
It will be understood that for some applications it may be
desirable to have individual electric motors for each drive shaft
16 in place of the single electric motor 100.
It will also be understood that jaw mechanisms capable of motions
different from those of the jaw mechanism 60 of FIGS. 1 and 8 may
be used in manipulators within the scope of the invention, as shown
for example in FIG. 11. In FIG. 11, a manipulator slave arm 550 is
shown identical in most respects to the slave arm 300 of FIG. 8,
identical parts being referred to by the same reference numerals.
The manipulator slave arm 550 differs from that of FIG. 8 only in
having a wrist mechanism 554, attached to the end of the forearm
330 remote from the elbow pivot pin 50, which enables a jaw
mechanism 556 to rotate Q about an, axis R--R which is at an angle
of 45.degree. to the longitudinal axis L--L of the jaw mechanism
556 and also at 45.degree. to the longitudinal axis of the forearm
330, at all times. In addition the jaw mechanism 556 can rotate G
about its own longitudinal axis L--L; and it can turn T about the
longitudinal axis of the forearm 330, this motion being brought
about by rotation of the forearm tube 530 as described above.
Referring now to FIG. 12, the wrist mechanism 554 comprises a first
open-ended casing portion 560, one end of which is attached to the
end of the forearm tube 530, and the other end of which defines a
cylindrical aperture 562 coaxial with the axis R--R. Rotatably
mounted by a bearing 564 in the aperture 562 is a second open-ended
casing portion 566 with a tubular extension 567 coaxial with axis
L--L. A spiral bevel gear 568 is defined around the open end of the
second casing portion 566 within the first casing portion 560 and
engages a spiral bevel gear 570 defined at the end of the tubular
drive shaft 516. Spiral bevel gears 572 and 574 are also defined at
the ends of the tubular drive shaft 518 and the axial drive shaft
542 respectively.
The bevel gear 572 engages a bevel gear 576 defined on one side of
a wheel 578 rotatable about the axis R--R and supported by a
bearing 580 within the open end of the second casing portion 566. A
spiral bevel gear 582 is defined on the other side of the wheel
578, and engages a bevel gear 584 at one end of a tubular drive
shaft 586 coaxial with axis L--L rotatably mounted within the
tubular extension 567 of the second casing portion 566 by spaced
apart bearings 588. The jaw mechanism 556 (a fragmentary portion
being shown broken away) is attached to the other end of the
tubular drive shaft 586.
The bevel gear 574 engages a spiral bevel gear 590 mounted on a
shaft 592 coaxial with axis R--R and rotatably supported at each
end by bearings 594 attached to the first and the second casing
portions 560 and 566. Another spiral bevel gear 596 is mounted on
the shaft 592 and engages a bevel gear 598 at one end of a jaw
drive shaft 600 extending along the axis L--L into the jaw
mechanism 556 and rotatably supported within the tubular drive
shaft 586 by spaced apart bearings 602.
In operation of the slave arm 550, rotation of the tubular drive
shaft 516 of the forearm 330 (which is brought about as described
above with respect to the slave arm 300 of FIG. 8) causes the
second casing portion 566 of the wrist mechanism 554, and hence
also the jaw mechanism 556, to rotate Q about the axis R--R.
Rotation of the tubular drive shaft 518 causes rotation of the
wheel 578 about the axis R--R, and hence rotation of the tubular
drive shaft 586 and rotation G of the jaw mechanism 556 about the
axis L--L. Rotation of the axial drive shaft 542 causes rotation of
the shaft 592 and hence of the jaw drive shaft 600, so as to
produce prehensile motion J of the jaws 62 of the jaw mechanism 556
(see FIG. 11).
The manipulator slave arm 550 of FIG. 11 has an advantage over the
slave arm 300 of FIG. 8 in that the joint between the forearm 330
and the jaw mechanism 556 can readily be sealed against ingress of
dust or other contaminants. As shown in FIG. 12, a rotary seal 610
is provided in the aperture 562, between the first casing portion
560 and the second casing portion 566, and a rotary seal 612 is
provided between the tubular extension 567 of the second casing
portion 566 and the tubular drive shaft 586. By inhibiting ingress
of dust into the wrist mechanism 554 and the forearm 330, wear of
the drives therein is minimised.
Although the manipulator slave arms 10, 300, 550 of FIGS. 1, 8 and
11 have been described as being secured to sealed plugs 12 in a
roof 13 of a radioactive cell 14, it will be understood that the
plugs 12 may be installed in a wall or a floor of a radioactive
cell 14, or some other containment. Alternatively, it will also be
understood that a manipulator within the scope of the invention may
be free-standing, or mounted on a mobile support for robotic use in
non-radioactive applications, for example in a plant assembly
line.
The foregoing manipulators may be controlled by the operator using
a master unit to provide electrical signals to the magnetic
particle clutches 104, 105. Such a master unit might be similar to
that described in British Patent Specification No. 2 058 009 A
(U.S. patent application Ser. No. 184,304, now U.S. Pat. No.
4,367,998).
* * * * *